Transceiver circuits are used in wireless communication applications such as cellular telephones, cordless telephones, and pagers. A transceiver has a receiver portion which receives modulated Radio Frequency (RF) signals and a transmitter portion which transmits modulated RF signals. The receiver portion receives a modulated RF signal and translates this signal to a lower Intermediate Frequency (IF) signal for demodulation. Typically, the received modulated RF signal is mixed with a Local Oscillator (LO) signal to generate the IF signal. The LO signal is a pure tone or unmodulated signal. The receiver portion includes an oscillator for generating the pure tone signal. In addition, a second oscillator is used in the transmitter portion for generating a modulated RF signal at a desired carrier frequency.
Because each transceiver has two oscillators, they typically occupy a large area and require complex circuitry. Due to RF interference, it is difficult to integrate two oscillators onto one integrated circuit. In addition, having two oscillators increases the amount of power consumed during normal operation compared to having one oscillator.
Accordingly, it would be advantageous to have a circuit for receiving and transmitting modulated RF signals which uses a single oscillator. It would be of further advantage for the circuit to be area and cost efficient.